JP2006063821A - Fuel supply amount control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably control fuel supply amount and suppress accidental fluctuation of a combustion state, in an internal combustion engine in which two fuel supply means are provided in upstream and downstream sides of an intake passage. <P>SOLUTION: In an intake pipe 11 of the engine 10, a primary injector 17 is provided in the vicinity of an intake port, and a secondary injector 18 is provided in the upstream side of a throttle valve 14. An ECU 50 performs feedback control of fuel injection amount from each of the injectors 17, 18 such that an air fuel ratio in each case corresponds to a target value. In particular, the ECU 50 imposes a predetermined restriction on the feedback control in accordance with a fuel injection state of the secondary injector 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel supply amount control device for an internal combustion engine in which two fuel supply means (injectors) are provided on an upstream side and a downstream side of an intake passage.

  Conventionally, for the purpose of improving the output of an internal combustion engine or the like, a primary injector as a first fuel supply means is provided in the vicinity of an intake port of an intake passage, and a secondary injector as a second fuel supply means is provided upstream of the primary injector. Are known, and the fuel injection amount of each injector is appropriately controlled in accordance with the operating state of the internal combustion engine. For example, in Patent Document 1, feedback control is performed on the fuel injection amount by the primary injector and open control is performed on the fuel injection amount by the secondary injector.

However, the following problems occur in the existing technology. That is, when fuel injection is performed by the secondary injector, fuel adheres over a wide range on the inner wall of the intake passage, resulting in disturbance of the air-fuel ratio. Therefore, the feedback correction amount fluctuates, and unexpected fluctuations occur in the fuel supply amount of the internal combustion engine. As a result, the combustion state fluctuates, which may cause problems such as deterioration of exhaust emission and torque fluctuation.
Japanese Patent No. 2704893

  The present invention relates to an internal combustion engine having two fuel supply means provided upstream and downstream of an intake passage, in which the fuel supply amount is suitably controlled to suppress unexpected fluctuations in the combustion state. The main purpose is to provide a supply amount control device.

  In an internal combustion engine in which the first fuel supply means and the second fuel supply means are provided on the downstream side and the upstream side of the intake passage, respectively, when the fuel supply ratio by the second fuel supply means increases or by the second fuel supply means The air-fuel ratio is disturbed immediately after the start of fuel supply or immediately after the fuel supply is stopped. This is due to the fact that when the fuel is supplied by the second fuel supply means, the fuel adheres to the inner wall of the intake passage over a wide range from the fuel supply position to the inlet of the combustion chamber. The quantity varies, and as a result, an unexpected variation in the combustion state occurs. In this situation, the inventors of the present application have confirmed that the above problem is greatly related to the fuel supply status of the second fuel supply means. In the present invention, when fuel is supplied by the second fuel supply means, a predetermined restriction is added to the feedback control according to the fuel supply status. Thereby, it is possible to eliminate or reduce the fluctuation of the feedback amount during the period in which the air-fuel ratio becomes unstable. As a result, in the internal combustion engine provided with two fuel supply means on the upstream side and the downstream side of the intake passage, it is possible to suitably control the fuel supply amount and suppress unexpected fluctuations in the combustion state.

Specifically, the following means can be considered as means for adding a restriction to the feedback control.
-Feedback control is prohibited when the fuel supply ratio of the second fuel supply means is equal to or greater than a predetermined value.
The feedback control is prohibited in at least one of a period from the start of fuel supply by the second fuel supply means until a predetermined time elapses and a period from the stop of fuel supply by the second fuel supply means until a predetermined time elapses. .
A feedback control gain in at least one of a period from the start of fuel supply by the second fuel supply means until a predetermined time elapses and a period from the stop of fuel supply by the second fuel supply means until a predetermined time elapses Reduce.

  That is, when the fuel supply ratio by the second fuel supply means is large, the amount of fuel adhering to the inner wall of the intake passage increases, thereby causing problems such as over-correction of the fuel supply amount due to disturbance of the air-fuel ratio. Further, immediately after the fuel supply of the second fuel supply means is started or immediately after it is stopped, the fuel adhering state of the inner wall of the intake passage changes, the air-fuel ratio becomes unstable, and the fuel supply amount is overcorrected. On the other hand, according to each of the above-mentioned means, it is possible to eliminate problems such as overcorrection of the fuel supply amount and stabilize the fuel supply amount control.

  When feedback control is prohibited, the fuel supply amount is open controlled instead. The fuel supply ratio of the second fuel supply means means the ratio of the fuel supply amount by the second fuel supply means to the total fuel supply amount.

  Here, how much fuel supplied by the second fuel supply means adheres to and departs from the inner wall of the intake passage varies depending on the operating state of the internal combustion engine (for example, cooling water temperature, load, etc.). Therefore, the predetermined time defined immediately after the start or stop of the fuel supply of the second fuel supply means may be variably set according to the operating state of the internal combustion engine.

  Further, it is preferable to variably set the control gain of the feedback control in accordance with the fuel supply ratio of the second fuel supply means within the period in which the fuel supply by the second fuel supply means is performed. As a result, during the fuel supply by the second fuel supply means, it is possible to perform the feedback control while suppressing the unexpected fluctuation of the combustion state.

  On the other hand, in feedback control, a control method is known in which the feedback correction amount is updated by performing skip processing and then performing integration processing as the air-fuel ratio is inverted between lean and rich. In the case of adopting this control method, it is preferable to variably set at least one of the integration amount and the skip amount used for calculating the feedback correction amount according to the fuel supply ratio of the second fuel supply means. Alternatively, in the feedback control, in the control device that performs the skip process as the air-fuel ratio is inverted between lean / rich, and then updates the feedback correction amount by performing the integration process subsequent to the hold process, It is preferable to variably set at least one of the integral amount, the skip amount, and the hold time used for calculating the feedback correction amount according to the fuel supply ratio of the second fuel supply means. With these configurations, feedback control can be performed in consideration of a response delay until the fuel supplied from the second fuel supply unit affects combustion.

  At this time, in particular, the larger the fuel supply ratio of the second fuel supply means, the smaller the integral amount, or the larger the fuel supply ratio of the second fuel supply means, the smaller the skip amount, or the fuel supply of the second fuel supply means. The larger the ratio, the longer the hold time. In this case, the fluctuation of the feedback correction amount is suppressed by reducing the integral amount, reducing the skip amount, or extending the hold time.

  Further, the feedback control may be prohibited within the period in which the fuel supply by the second fuel supply means is performed, and this configuration can also suppress unexpected fluctuations in the combustion state.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS An embodiment of the invention will be described below with reference to the drawings. In the present embodiment, an engine control system is constructed for a two-cylinder multi-cylinder gasoline engine that is an internal combustion engine. In the control system, an electronic control unit (hereinafter referred to as an ECU) is used as a center to control the fuel injection amount. Control and ignition timing control are to be implemented. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided in the uppermost stream portion of the intake pipe 11, and a throttle valve 14 is provided downstream thereof. The air cleaner 12 is provided with an intake air temperature sensor 13 for detecting the intake air temperature, and the throttle valve 14 is provided with a throttle opening sensor 15 for detecting the throttle opening. An intake pipe pressure sensor 16 for detecting the intake pipe pressure is provided on the downstream side of the throttle valve 14. Further, an electromagnetically driven primary injector 17 is attached in the vicinity of the intake port of the intake pipe 11, and an electromagnetically driven secondary injector 18 is also attached upstream of the throttle valve 14. The engine 10 is an independent intake type in which intake is performed independently for each cylinder, and a primary injector 17 and a secondary injector 18 are provided for each cylinder.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. The exhaust after combustion is discharged to the exhaust pipe 24 by the opening operation. A spark plug 25 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 25 at a desired ignition timing through an ignition device 26 including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 25, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the air-fuel ratio of the air-fuel mixture is detected on the upstream side of the catalyst 31 with exhaust as a detection target. An O2 sensor 32 is provided for detecting. The O2 sensor 32 is configured to output different electromotive force signals (O2 sensor signal VOX) depending on whether the air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio (stoichiometric). Further, the engine 10 includes a coolant temperature sensor 33 that detects a coolant temperature, and a crank angle sensor 34 that outputs a rectangular crank angle signal at predetermined crank angles (for example, at a cycle of 30 ° CA) as the engine 10 rotates. Is provided.

  In the fuel system, an in-tank type pump module 42 is provided in the fuel tank 41, and two delivery pipes 45 and 46 are connected to the pump module 42 via a fuel pipe 43. The pump module 42 is a pump device in which a pump main body, a fuel filter, a pressure regulator, and a return pipe are integrated. Fuel held at a predetermined pressure by the pump module 42 is supplied to the delivery pipes 45 and 46 via the fuel pipe 43. It is designed to be fed.

  The ECU 50 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The ECU 50 receives detection signals from the various sensors and other detection signals for the battery voltage VB. The ECU 50 executes various control programs stored in the ROM, thereby controlling the fuel injection time of the primary injector 17 and the secondary injector 18 and the ignition timing by the spark plug 25 based on the engine operating state. In particular, in fuel injection control, O2 feedback control is performed, and a feedback correction coefficient FAF is calculated based on a detection signal (O2 sensor signal VOX) of the O2 sensor 32, and the final fuel injection time is reflected by reflecting the FAF. Is calculated.

  FIG. 2 is a flowchart showing a routine for calculating the fuel injection time. This routine is executed by the ECU 50 at a predetermined crank angle cycle (180 ° CA cycle in the case of a four-cylinder engine).

  In FIG. 2, in step S101, the engine speed NE calculated based on the crank angle signal output from the crank angle sensor 34 is read. In step S102, the throttle opening VTA calculated from the detection value of the throttle opening sensor 15 is read. In step S103, the intake pressure PM calculated from the detected value of the intake pipe pressure sensor 16 is read. Thereafter, in step S104, a basic injection time TP @ for each cylinder is calculated based on the read operation information (NE, VTA, PM) (@ means each cylinder; the same applies hereinafter). At this time, in the low load range of the engine 10, the basic injection time TP @ is calculated using the engine speed NE and the intake pressure PM as parameters, and in the medium and high load range, the basic injection time is calculated using the engine speed NE and the throttle opening VTA as parameters. Calculate time TP @.

  Next, in step S105, for example, a map using the engine speed NE and the throttle opening degree VTA as parameters is used, and the injection ratio DES of the secondary injector 18 is calculated according to NE and VTA each time. The injection ratio DES is a ratio of the fuel injection amount of the secondary injector 18 to the total fuel injection amount. According to this map, the injection ratio DES is calculated as a larger value as the speed increases or the throttle opening increases (for example, the minimum value of DES is 0 and the maximum value is 1.0). is there).

Thereafter, in step S106, the invalid injection time TV of each injector 17, 18 is calculated based on the battery voltage VB, and in step S107, other correction coefficients K @ (intake air temperature correction, atmospheric pressure correction, etc.) are calculated. In step S108, a feedback correction coefficient FAF is calculated based on the O2 sensor signal VOX. Finally, in step S109, the following formulas (1) and (2) are used to calculate the final injection time TAU1 @ of the primary injector 17 and the final injection time TAU2 @ of the secondary injector 18.
TAU1 @ = TP @ * K @ * (1-DES) * FAF + TV (1)
TAU2 @ = TP @ * K @ * DES * FAF + TV (2)
Then, the ECU 50 outputs injector drive signals to the primary injector 17 and the secondary injector 18 based on the final injection times TAU1 @ and TAU2 @. Thereby, each injector 17 and 18 opens based on an injector drive signal, and fuel injection is implemented by each.

  3 and 4 show a subroutine for calculating the feedback correction coefficient FAF in step S108 of FIG.

  In FIG. 3, first, in steps S201 to S204, an execution condition for O2 feedback control is determined. That is, in step S201, it is determined whether or not a precondition for feedback control is satisfied based on the water temperature, the elapsed time after startup, or the like. In step S202, it is determined whether or not the injection ratio DES of the secondary injector 18 is smaller than a predetermined value Dth (for example, 0.5). In step S203, it is determined whether or not a predetermined time X1 has elapsed since the fuel injection by the secondary injector 18 was started. In step S204, it is determined whether or not a predetermined time X2 has elapsed since the fuel injection by the secondary injector 18 was stopped.

  If any of Steps S201 to S204 is not established, the process proceeds to Step S205, and after the feedback correction coefficient FAF is set to 1.0, this process ends. That is, in this case, the O2 feedback control is prohibited and the open control is performed instead. Further, when all of steps S201 to S204 are established, a series of FAF calculation processes after step S206 are performed. That is, in this case, execution of O2 feedback control is permitted.

  When execution of the O2 feedback control is permitted, in step S206, calculation parameters required for the FAF calculation are calculated based on the engine speed NE and the injection ratio DES of the secondary injector 18. Specifically, as calculation parameters, skip amounts KSI, KSD (KSI = increase, KSD = decrease) for increasing / decreasing the FAF value when the O2 sensor signal VOX is inverted between rich / lean and FAF after skipping Hold time KDL, KDR (KDL = lean, KDR = rich) to hold the value as it is, and gradually increase or decrease FAF value while O2 sensor signal VOX is maintained at rich value or lean value Integration amounts KII and KID (KII = when increasing, KID = when decreasing) are calculated.

  Each parameter is calculated according to the relationship shown in (a) to (f) of FIG. At this time, as shown in (a) and (b), the hold times KDL and KDR are calculated as larger values as the injection ratio DES of the secondary injector 18 is larger, and are calculated as smaller values as the engine speed NE is larger. The Further, as shown in (c) and (d), the integral amounts KII and KID are calculated as smaller values as the injection ratio DES of the secondary injector 18 is larger, and are calculated as smaller values as the engine rotational speed NE is larger. . This is because the response delay until the fuel injected from the secondary injector 18 affects the combustion is taken into consideration.

  Note that the skip amounts KSI and KSD do not change significantly even if the engine speed NE and the injection ratio DES of the secondary injector 18 change (can be fixed values). However, as shown in (e) and (f), as the injection ratio DES of the secondary injector 18 is larger, the skip amounts KSI and KSD may be reduced, thereby reducing the fluctuation of the combustion state accompanying the fluctuation of the FAF. can do. Conversely, as the injection ratio DES of the secondary injector 18 is larger, the skip amounts KSI and KSD may be increased, thereby shortening the FAF increase / decrease cycle and improving the catalyst purification performance.

  Thereafter, in step S207 of FIG. 4, it is determined whether or not the O2 sensor signal VOX is equal to or greater than a predetermined threshold value α for rich / lean determination. The threshold value α is, for example, 0.45 V. If VOX ≧ α, it is determined to be rich, and if VOX <α, it is determined to be lean.

  If VOX ≧ α (if the air-fuel ratio is rich), the process proceeds to step S208, and it is determined whether or not a predetermined delay time TDR has elapsed after the O2 sensor signal VOX is inverted from lean to rich. If the delay time TDR has elapsed, the process proceeds to step S209, and if not, the process proceeds to step S217. Note that the delay time TDR is a time caused by a delay in exhaust transportation, and may be variably set according to, for example, the engine speed NE (however, a fixed value is also acceptable).

  In step S209, it is determined whether or not the current process is the first time after the delay time TDR has elapsed. In the first case, the process proceeds to step S210, and the current value of FAF is calculated by subtracting the skip amount KSD from the previous value of the feedback correction coefficient FAF (FAF = FAF−KSD). If it is not the first time, the process proceeds to step S211, and it is determined whether or not the hold time KDR has elapsed after skipping. Then, FAF integration processing is permitted on the condition that the hold time KDR has elapsed, and in step S212, the integration value KID is subtracted from the previous value of FAF to calculate the current value of FAF (FAF = FAF−KID). ).

  On the other hand, if VOX <α (if the air-fuel ratio is lean), the process proceeds to step S213, where it is determined whether or not a predetermined delay time TDL has elapsed after the O2 sensor signal VOX is inverted from rich to lean. If the delay time TDL has elapsed, the process proceeds to step S214, and if not, the process proceeds to step S212. The delay time TDL is a time caused by the exhaust transport delay, similar to the TDR, and may be variably set according to, for example, the engine rotational speed NE (however, a fixed value is also acceptable).

  In step S214, it is determined whether or not the current process is the first time after the delay time TDL has elapsed. In the first case, the process proceeds to step S215, and the current value of FAF is calculated by adding the skip amount KSI to the previous value of the feedback correction coefficient FAF (FAF = FAF + KSI). If it is not the first time, the process advances to step S216 to determine whether or not the hold time KDL has elapsed after skipping. Then, FAF integration processing is permitted on the condition that the hold time KDL has elapsed, and in step S217, the integration value KII is added to the previous value of FAF to calculate the current value of FAF (FAF = FAF + KII).

  Next, the flow of the O2 feedback control process will be described more specifically using a time chart. FIG. 6 is a time chart showing how the injection modes of the primary / secondary injectors 17 and 18 change as the engine operating state changes. In FIG. 6, before the timing t1, the primary injector 17 is ON and the secondary injector 18 is OFF, and all the fuel is injected and supplied by the primary injector 17 (that is, the injection ratio DES of the secondary injector 18 is 0). is there).

  For example, when the throttle opening degree VTA increases due to the acceleration operation by the driver (in FIG. 6, when VTA exceeds the threshold value Vth at timing t1), the injection of the secondary injector 18 is started. At this time, as described above, the injection ratio DES of the secondary injector 18 is determined by the engine speed NE and the throttle opening VTA each time. However, in this example, the injection ratio DES is assumed to be less than the predetermined value Dth throughout the entire period shown.

  When fuel injection by the secondary injector 18 is started, O2 feedback control is prohibited during a period from the start of injection until the predetermined time X1 elapses. Then, after the timing t2 when the predetermined time X1 has elapsed, O2 feedback control is performed. Further, at the timing t3, the fuel injection of the secondary injector 18 is stopped as the throttle opening degree VTA decreases. At this time, O2 feedback control is prohibited during a period from when the injection of the secondary injector 18 stops until the predetermined time X2 elapses. Then, after the timing t4 when the predetermined time X2 has elapsed, the O2 feedback control is resumed.

  FIG. 7 is a time chart showing the behavior of the O2 sensor signal VOX and the feedback correction coefficient FAF during O2 feedback control. FIG. 7A shows the behavior of VOX and FAF when the secondary injector 18 is not injecting fuel. (B) shows the behavior of VOX and FAF when the secondary injector 18 is injecting fuel. (A) and (b) show skip amounts KSD1, KSD2, hold times KDR1, KDR2, and integral amounts KID1, KID2 when the O2 sensor signal VOX is a rich signal.

  The feedback correction coefficient FAF changes as shown in the figure by skip, hold (delay), and integration operations. At this time, comparing (a) and (b), the skip amount is KSD1> KSD2, the hold time is KDR1 <KDR2, and the integral amount is KID1> KID2. Therefore, the fluctuation of the feedback correction coefficient FAF is suppressed during secondary injector injection. That is, the control gain of the O2 feedback control is changed according to the fuel injection state of the secondary injector 18, and the O2 feedback control is performed in consideration of the response delay until the fuel injected from the secondary injector 18 affects the combustion.

  According to the present embodiment described above in detail, when the fuel injection by the secondary injector 18 is performed, a predetermined restriction is applied to the O2 feedback control in accordance with the fuel injection situation, so that the feedback correction is performed during the period when the air-fuel ratio becomes unstable. Variations in the coefficient FAF can be eliminated or reduced. As a result, the fuel injection amount can be suitably controlled, and unexpected fluctuations in the combustion state can be suppressed. Thereby, problems such as deterioration of exhaust emission and torque fluctuation can be solved.

  Specifically, when the injection ratio DES of the secondary injector 18 is greater than or equal to a predetermined value Dth, or during a period from the start of injection of the secondary injector 18 until the predetermined time X1 elapses until the predetermined time X2 elapses from the stop of injection. Since the O2 feedback control is prohibited during the period, problems such as overcorrection of the fuel injection amount can be solved, and the fuel injection amount control can be stabilized.

  In addition, since the calculation parameters (skip amount, hold time, integral amount) for FAF calculation are variably set according to the injection ratio DES of the secondary injector 18 at the time of secondary injector injection, the combustion state at the time of secondary injector injection O2 feedback control can be performed while suppressing unforeseen fluctuations.

(Second Embodiment)
In the first embodiment, the O2 feedback control is prohibited until a predetermined time elapses immediately after the start of injection by the secondary injector 18 or immediately after the stop of injection. In the present embodiment, Immediately after stopping the injection, the control gain of the O2 feedback control is reduced.

  FIG. 8 is a flowchart showing a subroutine for calculating the feedback correction coefficient FAF in the present embodiment, and this routine is executed in place of FIG. Note that after step S308 in FIG. 8 is executed, the process proceeds to step S207 in FIG. 4, and description thereof is omitted.

  In FIG. 8, in step S301, it is determined whether or not a precondition for feedback control is satisfied based on the water temperature, the elapsed time after startup, and the like. In step S302, the injection ratio DES of the secondary injector 18 is a predetermined value Dth (for example, 0. 0). It is determined whether it is smaller than 5). If any of steps S301 and S302 is NO, the process proceeds to step S303, the feedback correction coefficient FAF is set to 1.0, and the process is terminated. That is, in this case, the execution of O2 feedback control is prohibited. If both steps S301 and S302 are YES, the process proceeds to step S304.

  In step S304, it is determined whether or not a predetermined time Y1 has elapsed since the fuel injection by the secondary injector 18 was started. In step S305, it is determined whether or not a predetermined time Y2 has elapsed since the fuel injection by the secondary injector 18 was stopped. If both steps S304 and S305 are YES, the process proceeds to step S306, and the FAF calculation parameters (skip amounts KSI, KSD, hold) based on the engine speed NE and the injection ratio DES of the secondary injector 18 using the relationship shown in FIG. Times KDL, KDR, integral amounts KII, KID) are calculated.

  Further, if it is a period until the predetermined time Y1 elapses after the injection of the secondary injector 18, the calculation parameters (skip amounts KSI, KSD, hold times KDL, KDR, integration amount KII, the injection start switching time in step S307). (KID) is calculated and the calculation parameters (skip amounts KSI, KSD, hold times KDL, KDR, and the like at the time of injection stop switching in step S308, if the predetermined time Y2 elapses after the injection of the secondary injector 18 is completed. Integration amounts KII, KID) are calculated.

  In this case, the calculation parameter at the time of injection start switching and at the time of injection stop switching is changed so as to lower the control gain compared to the calculation parameter calculated in step S306. FIG. 9 shows differences in parameters when the injection ratio DES of the secondary injector 18 is the same. In FIG. 9, a solid line P1 indicates a normal parameter value (calculated value in step S306), a dotted line P2 indicates a parameter value at the time of injection start switching, and an alternate long and short dash line P3 indicates a parameter value at the time of injection stop switching.

  As shown in FIGS. 9A and 9B, the hold times KDL and KDR at the time of injection start switching and at the time of injection stop switching are set longer than the normal time (P1), and the parameter values ( P2) is a value slightly smaller than the parameter value (P3) at the time of injection stop switching. Further, as shown in (c) and (d), the integral amounts KII and KID at the time of the injection start switching and the injection stop switching are set smaller than the normal time (P1), and the parameter value (P2 at the time of the injection start switching). ) Is a value slightly larger than the parameter value (P3) at the time of injection stop switching. Furthermore, as shown in (e) and (f), the skip amounts KSI and KSD at the time of injection start switching and at the time of injection stop switching are set smaller than the normal time (P1), and the parameter value (P2 at the time of injection start switching). ) Is a value slightly larger than the parameter value (P3) at the time of injection stop switching.

  As described above, according to the second embodiment, the control gain of the O2 feedback control is reduced in the period in which the disturbance of the air-fuel ratio is likely to occur, such as immediately after the injection of the secondary injector 18 is started or immediately after the injection is stopped. Inconveniences such as overcorrection can be eliminated, and fuel supply amount control can be stabilized.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, skip amounts KSI, KSD, hold times KDL, KDR, and integral amounts KII, KID are variably set based on the engine speed NE and the injection ratio DES of the secondary injector 18 as FAF calculation parameters. At least one of them may be variably set and the others may be fixed values. Further, the same parameter value may be used for the rich time and the lean time.

  In the above embodiment, the feedback correction coefficient FAF is updated by skip, hold (delay), and integration operations. However, the feedback correction coefficient FAF may be updated only by skip and integration operations. This is equivalent to setting the hold time to zero. In such a case, the behavior of the O2 sensor signal VOX and the feedback correction coefficient FAF during the O2 feedback control is shown in FIG. 10A shows the behavior of VOX and FAF when the secondary injector 18 is not injecting fuel, and FIG. 10B shows the behavior of VOX and FAF when the secondary injector 18 is injecting fuel. Show. Note that (a) and (b) show skip amounts KSD1 and KSD2 and integral amounts KID1 and KID2 when the O2 sensor signal VOX is a rich signal.

  Comparing (a) and (b) of FIG. 10, the skip amount is KSD1> KSD2, and the integral amount is KID1> KID2. Therefore, the fluctuation of the feedback correction coefficient FAF is suppressed during secondary injector injection. That is, the control gain of the O2 feedback control is changed according to the fuel injection state of the secondary injector 18, and the O2 feedback control is performed in consideration of the response delay until the fuel injected from the secondary injector 18 affects the combustion.

  In the above embodiment, the O2 feedback control is prohibited or the control gain of the O2 feedback control is reduced in the period immediately after the start of injection by the secondary injector 18 and immediately after the stop of injection. However, this may be changed. . For example, the O2 feedback control may be prohibited or the control gain of the O2 feedback control may be reduced in any period immediately after the start of injection by the secondary injector 18 or immediately after the stop of injection. Further, after the start of the injection of the secondary injector 18 (or after the stop of the injection), the O2 feedback control is prohibited or the control gain of the O2 feedback control is reduced in a period until a predetermined number of fuel injections are performed. good.

  In the above embodiment, the air-fuel ratio feedback control is performed using the O2 sensor that outputs the electromotive force signal (VOX) different between rich and lean at the theoretical air-fuel ratio as a boundary. The air-fuel ratio feedback control may be implemented using an A / F sensor that linearly detects the oxygen concentration in the air. In this case, a feedback correction coefficient FAF is calculated according to the deviation between the air-fuel ratio detected by the A / F sensor and the target air-fuel ratio, and air-fuel ratio feedback control is performed using the FAF. Even in such a configuration, when the fuel injection by the secondary injector 18 is performed, a predetermined restriction is applied to the air-fuel ratio feedback control according to the fuel injection situation, so that the feedback correction coefficient FAF is reduced during the period when the air-fuel ratio becomes unstable. Variation can be reduced. As a result, the fuel injection amount can be suitably controlled, and unexpected fluctuations in the combustion state can be suppressed.

  Predetermined times X1 and X2 (Y1 and Y2 in the second embodiment) defined immediately after the start of injection of the secondary injector 18 or immediately after the stop of injection are set to engine operating conditions such as cooling water temperature, load, and engine speed, for example. Depending on this, it may be variably set. The amount of fuel adhering to the intake pipe inner wall by the secondary injector 18 and the amount of fuel adhering to the fuel change according to the engine operating state, thereby changing the degree of influence on the air-fuel ratio. In such a case, by changing the predetermined times X1, X2, etc. as described above, it is possible to suitably suppress the fluctuation of the fuel state due to the disturbance of the air-fuel ratio.

  Air-fuel ratio feedback control may be prohibited throughout the entire period in which fuel injection is performed by the secondary injector 18, and unexpected fluctuations in the combustion state can also be suppressed by this configuration. That is, during the fuel injection period by the secondary injector 18, open control is performed instead of feedback control.

  In the above embodiment, the engine 10 is of the independent intake type, and the primary injector 17 and the secondary injector 18 are provided for each intake pipe of each cylinder. However, this configuration may be changed. For example, in an engine provided with an intake manifold, a primary injector (first fuel supply means) may be provided in a branch passage portion communicating with each cylinder, and a secondary injector (second fuel supply means) may be provided in a collecting portion. That is, in this case, the secondary injector is used in common for all cylinders. In addition to a motorcycle engine, the present invention may be embodied in a four-wheeled vehicle engine.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a flowchart which shows a fuel injection time calculation routine. It is a flowchart which shows a feedback correction coefficient calculation routine. FIG. 4 is a flowchart illustrating a feedback correction coefficient calculation routine following FIG. 3. FIG. 6 is a relationship diagram for calculating FAF calculation parameters. It is a time chart which shows the change of the injection mode of each injector. It is a time chart which shows the behavior of O2 sensor signal VOX and feedback correction coefficient FAF at the time of O2 feedback control. It is a flowchart which shows the feedback correction coefficient calculation routine in 2nd Embodiment. FIG. 6 is a relationship diagram for calculating FAF calculation parameters. It is a time chart which shows the behavior of O2 sensor signal VOX and feedback correction coefficient FAF at the time of O2 feedback control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine as an internal combustion engine, 11 ... Intake pipe, 17 ... Primary injector as 1st fuel supply means, 18 ... Secondary injector as 2nd fuel supply means, 32 ... O2 sensor, 50 ... ECU.

Claims (12)

The first and second fuel supplies are applied to the internal combustion engine provided with the first fuel supply means and the second fuel supply means on the downstream side and the upstream side of the intake passage, respectively, so that the air-fuel ratio in each case matches the target value. In a fuel supply amount control apparatus for an internal combustion engine that performs feedback control of a fuel supply amount by means,
A fuel supply amount control device for an internal combustion engine, wherein when the fuel is supplied by the second fuel supply means, a predetermined restriction is applied to the feedback control according to the fuel supply status.   2. The fuel supply amount control device for an internal combustion engine according to claim 1, wherein the feedback control is prohibited when a fuel supply ratio of the second fuel supply unit is equal to or greater than a predetermined value.   The feedback control is performed in at least one of a period until a predetermined time elapses after the fuel supply start of the second fuel supply means and a period until a predetermined time elapses after the fuel supply stop of the second fuel supply means. 3. The fuel supply amount control device for an internal combustion engine according to claim 1, wherein the fuel supply amount control device is prohibited.   The feedback control is performed in at least one of a period until a predetermined time elapses after the fuel supply start of the second fuel supply means and a period until a predetermined time elapses after the fuel supply stop of the second fuel supply means. 3. The fuel supply amount control apparatus for an internal combustion engine according to claim 1, wherein the control gain is reduced.   5. The internal combustion engine according to claim 3, wherein the predetermined time defined immediately after the start or stop of the fuel supply of the second fuel supply means is variably set according to the operating state of the internal combustion engine. Fuel supply control device.   The control gain of the feedback control is variably set according to the fuel supply ratio of the second fuel supply means within a period in which the fuel supply by the second fuel supply means is performed. The fuel supply amount control device for an internal combustion engine according to any one of claims 5 to 6. A means for detecting whether the air-fuel ratio is leaner or richer than the stoichiometric air-fuel ratio is provided, and during the feedback control, feedback is performed by performing skip processing and then integrating processing as the air-fuel ratio is reversed between lean and rich. In the control device that updates the correction amount,
6. The integral amount or the skip amount used for calculating the feedback correction amount is variably set according to a fuel supply ratio of the second fuel supply unit. A fuel supply amount control device for an internal combustion engine. A means for detecting whether the air-fuel ratio is leaner or richer than the stoichiometric air-fuel ratio is provided. During the feedback control, skip processing is performed as the air-fuel ratio is reversed between lean and rich, and then integration is performed following the hold processing. In a control device that updates the feedback correction amount by performing processing,
6. The variable amount of at least one of an integral amount, a skip amount, and a hold time used for calculating the feedback correction amount is set in accordance with a fuel supply ratio of the second fuel supply means. A fuel supply amount control device for an internal combustion engine according to claim 1.   9. The fuel supply amount control apparatus for an internal combustion engine according to claim 8, wherein the hold time is lengthened as the fuel supply ratio of the second fuel supply means increases.   10. The fuel supply amount control apparatus for an internal combustion engine according to claim 7, wherein the integral amount is reduced as the fuel supply ratio of the second fuel supply means increases.   11. The fuel supply amount control apparatus for an internal combustion engine according to claim 7, wherein the skip amount is reduced as the fuel supply ratio of the second fuel supply means increases.   2. The fuel supply amount control device for an internal combustion engine according to claim 1, wherein the feedback control is prohibited within a period in which fuel is supplied by the second fuel supply unit.

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